/*
 * File: Base64Coder.java
 * 
 * This file is part of POSIT, Portable Open Search and Identification Tool.
 *
 * <p>
 * A Base64 Encoder/Decoder.
 * This class is used to encode and decode data in Base64 format as described in RFC 1521.
 *
 * <p>
 * This is "Open Source" software and released under the <a href="http://www.gnu.org/licenses/lgpl.html">GNU/LGPL</a> license.<br>
 * It is provided "as is" without warranty of any kind.<br>
 * Copyright 2003: Christian d'Heureuse, Inventec Informatik AG, Switzerland.<br>
 * Home page: <a href="http://www.source-code.biz">www.source-code.biz</a><br>
 *
 * <p>
 * Version history:<br>
 * 2003-07-22 Christian d'Heureuse (chdh): Module created.<br>
 * 2005-08-11 chdh: Lincense changed from GPL to LGPL.<br>
 * 2006-11-21 chdh:<br>
 *  &nbsp; Method encode(String) renamed to encodeString(String).<br>
 *  &nbsp; Method decode(String) renamed to decodeString(String).<br>
 *  &nbsp; New method encode(byte[],int) added.<br>
 *  &nbsp; New method decode(String) added.<br>
 *  
 *  You should have received a copy of the GNU LGPL along with this program; 
 * if not visit http://www.gnu.org/licenses/lgpl.html.
 */

package org.hfoss.third;

public class Base64Coder {

	// Mapping table from 6-bit nibbles to Base64 characters.
	private static char[]    map1 = new char[64];
	static {
		int i=0;
		for (char c='A'; c<='Z'; c++) map1[i++] = c;
		for (char c='a'; c<='z'; c++) map1[i++] = c;
		for (char c='0'; c<='9'; c++) map1[i++] = c;
		map1[i++] = '+'; map1[i++] = '/'; }

	// Mapping table from Base64 characters to 6-bit nibbles.
	private static byte[]    map2 = new byte[128];
	static {
		for (int i=0; i<map2.length; i++) map2[i] = -1;
		for (int i=0; i<64; i++) map2[map1[i]] = (byte)i; }

	/**
	 * Encodes a string into Base64 format.
	 * No blanks or line breaks are inserted.
	 * @param s  a String to be encoded.
	 * @return   A String with the Base64 encoded data.
	 */
	public static String encodeString (String s) {
		return new String(encode(s.getBytes())); }

	/**
	 * Encodes a byte array into Base64 format.
	 * No blanks or line breaks are inserted.
	 * @param in  an array containing the data bytes to be encoded.
	 * @return    A character array with the Base64 encoded data.
	 */
	public static char[] encode (byte[] in) {
		return encode(in,in.length); }

	/**
	 * Encodes a byte array into Base64 format.
	 * No blanks or line breaks are inserted.
	 * @param in   an array containing the data bytes to be encoded.
	 * @param iLen number of bytes to process in <code>in</code>.
	 * @return     A character array with the Base64 encoded data.
	 */
	public static char[] encode (byte[] in, int iLen) {
		int oDataLen = (iLen*4+2)/3;       // output length without padding
		int oLen = ((iLen+2)/3)*4;         // output length including padding
		char[] out = new char[oLen];
		int ip = 0;
		int op = 0;
		while (ip < iLen) {
			int i0 = in[ip++] & 0xff;
			int i1 = ip < iLen ? in[ip++] & 0xff : 0;
			int i2 = ip < iLen ? in[ip++] & 0xff : 0;
			int o0 = i0 >>> 2;
			int o1 = ((i0 &   3) << 4) | (i1 >>> 4);
			int o2 = ((i1 & 0xf) << 2) | (i2 >>> 6);
			int o3 = i2 & 0x3F;
			out[op++] = map1[o0];
			out[op++] = map1[o1];
			out[op] = op < oDataLen ? map1[o2] : '='; op++;
			out[op] = op < oDataLen ? map1[o3] : '='; op++; }
		return out; }

	/**
	 * Decodes a string from Base64 format.
	 * @param s  a Base64 String to be decoded.
	 * @return   A String containing the decoded data.
	 * @throws   IllegalArgumentException if the input is not valid Base64 encoded data.
	 */
	public static String decodeString (String s) {
		return new String(decode(s)); }

	/**
	 * Decodes a byte array from Base64 format.
	 * @param s  a Base64 String to be decoded.
	 * @return   An array containing the decoded data bytes.
	 * @throws   IllegalArgumentException if the input is not valid Base64 encoded data.
	 */
	public static byte[] decode (String s) {
		return decode(s.toCharArray()); }

	/**
	 * Decodes a byte array from Base64 format.
	 * No blanks or line breaks are allowed within the Base64 encoded data.
	 * @param in  a character array containing the Base64 encoded data.
	 * @return    An array containing the decoded data bytes.
	 * @throws    IllegalArgumentException if the input is not valid Base64 encoded data.
	 */
	public static byte[] decode (char[] in) {
		int iLen = in.length;
		if (iLen%4 != 0) throw new IllegalArgumentException ("Length of Base64 encoded input string is not a multiple of 4.");
		while (iLen > 0 && in[iLen-1] == '=') iLen--;
		int oLen = (iLen*3) / 4;
		byte[] out = new byte[oLen];
		int ip = 0;
		int op = 0;
		while (ip < iLen) {
			int i0 = in[ip++];
			int i1 = in[ip++];
			int i2 = ip < iLen ? in[ip++] : 'A';
			int i3 = ip < iLen ? in[ip++] : 'A';
			if (i0 > 127 || i1 > 127 || i2 > 127 || i3 > 127)
				throw new IllegalArgumentException ("Illegal character in Base64 encoded data.");
			int b0 = map2[i0];
			int b1 = map2[i1];
			int b2 = map2[i2];
			int b3 = map2[i3];
			if (b0 < 0 || b1 < 0 || b2 < 0 || b3 < 0)
				throw new IllegalArgumentException ("Illegal character in Base64 encoded data.");
			int o0 = ( b0       <<2) | (b1>>>4);
			int o1 = ((b1 & 0xf)<<4) | (b2>>>2);
			int o2 = ((b2 &   3)<<6) |  b3;
			out[op++] = (byte)o0;
			if (op<oLen) out[op++] = (byte)o1;
			if (op<oLen) out[op++] = (byte)o2; }
		return out; }

	// Dummy constructor.
	private Base64Coder() {}

} // end class Base64Coder
